U.S. patent number 4,556,477 [Application Number 06/662,660] was granted by the patent office on 1985-12-03 for highly siliceous porous crystalline material zsm-22 and its use in catalytic dewaxing of petroleum stocks.
This patent grant is currently assigned to Mobil Oil Corporation. Invention is credited to Francis G. Dwyer.
United States Patent |
4,556,477 |
Dwyer |
December 3, 1985 |
**Please see images for:
( Certificate of Correction ) ** |
Highly siliceous porous crystalline material ZSM-22 and its use in
catalytic dewaxing of petroleum stocks
Abstract
A new zeolite, designated ZSM-22, is disclosed and claimed. The
new zeolite has the composition, in the anhydrous state, expressed
in terms of mole ratios of oxides as follows: wherein Q.sub.2 O is
the oxide form of an organic compound containing an element of
Group 5-B (as defined in the Table of the Elements--National Bureau
of Standards, Fischer Scientific Co. Catalog No. 5-702-10), e.g., N
or P, preferably N, containing at least one alkyl or aryl group
having at least 2 carbon atoms, M is an alkali or alkaline earth
metal having a valence n, e.g., Na, K, Cs or Li and wherein
x=0.01-2.0, y=0-2.0, z=0-5, and L=Al. The new zeolite, ZSM-22, can
be used in catalytic dewaxing of petroleum stocks in the presence
or absence of added hydrogen.
Inventors: |
Dwyer; Francis G. (West
Chester, PA) |
Assignee: |
Mobil Oil Corporation (New
York, NY)
|
Family
ID: |
27079980 |
Appl.
No.: |
06/662,660 |
Filed: |
October 19, 1984 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
587327 |
Mar 7, 1984 |
|
|
|
|
373451 |
Apr 30, 1982 |
|
|
|
|
Current U.S.
Class: |
208/111.15;
208/111.25 |
Current CPC
Class: |
C10G
45/64 (20130101); B01J 29/7042 (20130101) |
Current International
Class: |
B01J
29/70 (20060101); B01J 29/00 (20060101); C10G
45/64 (20060101); C10G 45/58 (20060101); C10G
047/16 () |
Field of
Search: |
;208/111,109,118,120,28 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gantz; D. E.
Assistant Examiner: Pal; A.
Attorney, Agent or Firm: McKillop; Alexander J. Gilman;
Michael G. Kenehan, Jr.; Edward F.
Claims
WHAT IS CLAIMED IS:
1. A process for catalytic dewaxing of petroleum stocks comprising
contacting the petroleum stocks, in the presence or absence of
added hydrogen, with a ZSM-22 zeolite catalyst under conditions
including a temperatue of about 300-1000.degree. F., a pressure of
0-2000 psig, a liquid hourly space velocity of 0.1 to 10 and a
hydrogen to hydrocarbon ratio of about 0 to 25:1.
2. A process according to claim 1, wherein said petroleum stock is
a gas oil.
3. A process for catalytic dewaxing of a lube stock comprising
contacting the lube stock, in the presence of added hydrogen, with
a ZSM-22 zeolite catalyt under conditions including a temperature
of between about 500.degree. F. and about 675.degree. F., a
pressure of between about 100 and about 3000 psig, a liquid hourly
space velocity between about 0.1 and about 10 and a hydrogen to
feed ratio of from about 400 to about 8000 standard cubic feed of
hydrogen per barrel of feed.
4. A process according to claim 3, wherein said conditions include
a pressure between about 200 and about 1000 psig.
5. A process according to claim 4, wherein said conditions include
a liquid hourly space velocity between about 0.5 and 4.0.
6. A process according to claim 5, wherein said conditions include
a hydrogen to feed ratio of from about 800 to about 4000 standard
cubic feed of hydrogen per barrel of feed.
Description
This is a continuation of copending application Ser. No. 587,327,
filed on Mar. 7, 1984 now abandoned which is a divisional
application of application Ser. No. 373451, pending.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a novel siliceous porous crystalline
material.
2. Description of the Related Art
Zeolitic materials, both natural and synthetic, have been
demonstrated in the past to have catalytic properties for various
types of hydrocarbon conversion. Certain zeolitic materials are
ordered, porous crystalline aluminosilicates having a definite
crystalline structure as determined by X-ray diffraction, within
which there are a large number of smaller cavities which may be
interconnected by a number of still smaller channels or pores.
These cavities and pores are uniform in size within a specific
zeolitic material. Since the dimensions of these pores are such as
to accept for adsorption molecules of certain dimensions while
rejecting those of larger dimensions, these materials have come to
be known as "molecular sieves" and are utilized in a variety of
ways to take advantage of these properties.
Such molecular sieves, both natural and synthetic, include a wide
variety of positive ion-containing crystalline aluminosilicates.
These aluminosilicates can be described as having a rigid
three-dimensional framework of SiO.sub.4 and AlO.sub.4 in which the
tetrahedra are cross-linked by the sharing of oxygen atoms whereby
the ratio of the total aluminum and silicon atoms to oxygen atoms
is 1:2. The electrovalence of the tetrahedra containing aluminum is
balanced by the inclusion in the crystal of a cation, for example
an alkali metal or an alkaline earth metal cation. This can be
expressed by the relationship of aluminum to the cations, wherein
the ratio of aluminum to the number of various cations, such as
Ca/2, Sr/2, Na, K, Cs or Li, is equal to unity. One type of cation
may be exchanged either entirely or partially with another type of
cation utilizing ion exchange techniques in a conventional manner.
By means of such cation exchange, it has been possible to vary the
properties of a given aluminosilicate by suitable selection of the
cation. The spaces between the tetrahedra are occupied by molecules
of water prior to dehydration.
Prior art techniques have resulted in the formation of a great
variety of synthetic aluminosilicates. The aluminosilicates have
come to be designated by letter or other convenient symbols, as
illustrated by zeolite A (U.S. Pat. No. 2,882,243), zeolite X (U.S.
Pat. No. 2,882,244), zeolite Y (U.S. Pat. No. 3,130,007), zeolite
ZK-5 (U.S. Pat. No. 3,247,195), zeolite ZK-4 (U.S. Pat. No.
3,314,752), zeolite ZSM-5 (U.S. Pat. No. 3,702,886), zeolite ZSM-11
(U.S. Pat. No. 3,709,979), zeolite ZSM-12 (U.S. Pat. No.
3,832,449), zeolite ZSM-20 (U.S. Pat. No. 3,972,983), ZSM-35 (U.S.
Pat. No. 4,016,245), zeolites ZSM-21 and ZSM-38 (U.S. Pat. No.
4,046,859), and zeolite ZSM-23 (U.S. Pat. No. 4,076,842).
The SiO.sub.2 /Al.sub.2 O.sub.3 ratio of a given zeolite is often
variable. For example, zeolite X can be synthesized with SiO.sub.2
/Al.sub.2 O.sub.3 ratios of from 2 to 3; zeolite Y, from 3 to about
6. In some zeolites, the upper limit of the SiO.sub.2 /Al.sub.2
O.sub.3 ratio is unbounded. ZSM-5 is one such example wherein the
SiO.sub.2 /Al.sub.2 O.sub.3 ratio is at least 5, up to infinity.
U.S. Pat. No. 3,941,871, now No. Re. 29,948, the entire contents of
which are incorporated herein by reference, discloses a porous
crystalline silicate zeolite made from a reaction mixture
containing no deliberately added alumina in the recipe and
exhibiting the X-ray diffraction pattern characteristic of ZSM-5
type zeolites. U.S. Pat. Nos. 4,061,724, 4,073,865 and 4,104,294,
the entire contents of all three patents being incorporated herein
by reference, describe crystalline silica compositions of varying
alumina and metal content.
SUMMARY OF THE INVENTION
The present invention is directed to a novel highly siliceous
porous crystalline material. The crystalline material of this
invention has been designated as the zeolite ZSM-22 and it has a
characteristic X-ray diffraction pattern, as set forth in Table 1,
discussed below.
The highly siliceous material of this invention comprises
crystalline, three-dimensional continuous framework
silicon-containing structures or crystals which result when all the
oxygen atoms in the tetrahedra are mutually shared between
tetrahedral atoms of silicon or aluminum, and which can exist with
a network of mostly SiO.sub.2, i.e., exclusive of any
intracrystalline cations. Similar structures form building blocks
of materials such as quartz, cristobalite and a long list of
zeolite structures such as ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35,
ZSM-38, ZSM-48 (described in a copending U.S. application Ser. No.
56,754, filed July 12, 1979), mordenite and perhaps even faujasite.
Not all zeolite structures are known to exist at this time in
predominantly SiO.sub.2 --containing compositions--so the above
class of materials does not presently include zeolites such as
zeolite A.
The zeolite of the present invention also contains a relatively
minor amount of Al.sub.2 O.sub.3 and can produce a product with a
SiO.sub.2 to Al.sub.2 O.sub.3 mole ratio of about 20 to about
.infin.. In the as-synthesized form, the ZSM-22 has a calculated
composition, in terms of moles of oxides, after dehydration, per
100 moles of silica, as follows:
wherein Q.sub.2 O is the oxide form of an organic compound
containing an element of Group 5-B (as defined in the Table of the
Elements--National Bureau of Standards, Fischer Scientific Co.
Catalog No. 5-702-10), e.g., N or P, preferably N, containing at
least one alkyl or aryl group having at least 2 carbon atoms, M is
an alkali metal or an alkaline earth metal having a valence n, and
wherein x=0.01-2.0, y=0-2.0, z=0-5, and L=A1.
ZSM-22 can further be identified by its sorptive characteristics
and its X-ray diffraction pattern. The original cations of the
as-synthesized ZSM-22 may be replaced at least in part by other
ions using conventional ion exchange techniques. It may be
necessary to precalcine the ZSM-22 zeolite crystals prior to ion
exchange. The replacing ions introduced to replace the original
alkali, alkaline earth and/or organic cations may be any that are
desired so long as they can pass through the channels within the
zeolite crystals. Desired replacing ions are those of hydrogen,
rare earth metals, metals of Groups IB, IIA, IIB, IIIA, IIIB, IVA,
IVB, VIB and VIII of the Periodic Table. Among the metals, those
particularly preferred are rare earth metals, manganese, zinc and
those of Group VIII of the Periodic Table.
ZSM-22 zeolite described and claimed herein has a definite X-ray
diffraction pattern, set forth below in Table I, which
distinguishes it from other crystalline materials.
TABLE I ______________________________________ Most Significant
Lines of ZSM-22 Interplanar d-spacings (.ANG.) Relative Intensity
(I/Io) ______________________________________ 10.9 .+-. 0.2 M-VS
8.7 .+-. 0.16 W 6.94 .+-. 0.10 W-M 5.40 .+-. 0.08 W 4.58 .+-. 0.07
W 4.36 .+-. 0.07 VS 3.68 .+-. 0.05 VS 3.62 .+-. 0.05 S-VS 3.47 .+-.
0.04 M-S 3.30 .+-. 0.04 W 2.74 .+-. 0.02 W 2.52 .+-. 0.02 W
______________________________________
These values were determined by standard techniques. The radiation
was the K-alpha doublet of copper and a diffractometer equipped
with a scintillation counter and an associated computer was used.
The peak heights, I, and the positions as a function of 2 theta,
where theta is the Bragg angle, were determined using algorithms on
the computer associated with the spectrometer. From these, the
relative intensities, 100 I/I.sub.o, where I.sub.o is the intensity
of the strongest line or peak, and d (obs.) the interplanar spacing
in .ANG., corresponding to the recorded lines, were determined. In
Table I, the relative intensities are given in terms of the symbols
vs=very strong, s=strong, m=medium, w=weak, etc. It should be
understood that this X-ray diffraction pattern is characteristic of
all the species of ZSM-22 zeolite compositions. Ion exchange of the
alkali metal cations with other ions results in a zeolite which
reveals substantially the same X-ray diffraction pattern with some
minor shifts in interplanar spacing and variation in relative
intensity. Other minor variations can occur, depending on the
silica to alumina ratio of the particular sample, as well as its
degree of thermal treatment.
The zeolite of this invention freely sorbs normal hexane and has a
pore dimension greater than about 4 Angstroms. In addition, the
structure of the zeolite must provide constrained access to larger
molecules. It is sometimes possible to judge from a known crystal
structure whether such constrained access exists. For example, if
the only pore windows in a crystal are formed by 8-membered rings
of silicon and aluminum atoms, then access by molecules of larger
cross-section than normal hexane is excluded and the zeolite is not
of the desired type. Windows of 10-membered rings are preferred,
although, in some instances, excessive puckering or pore blockage
may render these zeolites ineffective. Twelve-membered rings do not
generally appear to offer sufficient constraint to produce the
advantageous hydrocarbon conversions, although puckered structures
exist such as TMA offretite which is known effective zeolite. Also,
such twelve-membered structures can be conceived that may be
operative due to pore blockage or other causes.
Rather than attempt to judge from crystal structure whether or not
a zeolite possesses the necessary constrained access, a simple
determination of the "constraint index" may be made by passing
continuously a mixture of an equal weight of normal hexane and
3-methylpentane over a sample of zeolite at atmospheric pressure
according to the following procedure. A sample of the zeolite, in
the form of pellets or extrudate, is crushed to a particle size
about that of coarse sand and mounted in a glass tube. Prior to
testing, the zeolite is treated with a stream of air at
1000.degree. F. for at least 15 minutes. The zeolite is then
flushed with helium and the temperature adjusted between
550.degree. F. (288.degree. C.) and 950.degree. F. (510.degree. C.)
to give an overall conversion between 10% and 60%. The mixture of
hydrocarbons is passed at a 1 liquid hourly spaced velocity (LHSV),
i.e., 1 volume of liquid hydrocarbon per volume of zeolite per hour
over the zeolite with a helium dilution to give a helium to total
hydrocarbon mole ratio of 4:1. After 20 minutes on stream, a sample
of the effluent is taken and analyzed, most conveniently by gas
chromatography, to determine the fraction remaining unchanged for
each of the two hydrocarbons.
The "constraint index" is calculated as follows: ##EQU1##
The constraint index approximates the ratio of the cracking rate
constants for the two hydrocarbons. Zeolites of the present
invention are those having a constraint index in the approximate
range of 1 to 12, preferably 1 to 5, and most preferably about 2.5
to about 3.0. Constraint Index (CI) values for some typical
zeolites are:
______________________________________ Zeolite C.I.
______________________________________ ZSM-5 8.3 ZSM-11 8.7 ZSM-12
2 ZSM-23 9.1 ZSM-38 2 ZSM-35 4.5 Clinoptilolite 3.4 TMA Offretite
3.7 Beta 0.6 ZSM-4 0.5 H--Zelon 0.4 REY 0.4 Amorphous
Silica-Alumina 0.6 (non-zeolite) Erionite 38
______________________________________
It is to be realized that the above constraint index values
typically characterize the specified zeolites but that these are
the cumulative result of several variables used in determination
and calculation thereof. Thus, for a given zeolite depending on the
temperature employed within the aforenoted range of 550.degree. F.
to 950.degree. F., with accompanying conversion between 10% and
60%, the constraint index may vary within the indicated approximate
range of 1 to 12. Likewise, other variables such as the crystal
size of the zeolite, the presence of possible occluded contaminants
and binders intimately combined with the zeolite, may affect the
constraint index. It will accordingly be understood by those
skilled in the art that the constraint index, as utilized herein,
while affording a highly useful means for characterizing the
zeolites of interest is approximate, taking into consideration the
manner of its determination; with probability, in some instances,
of compounding variable extremes.
While the above experimental procedure will enable one to achieve
the desired overall conversion of 10 to 60% for most catalyst
samples and represents preferred conditions, it may occasionally be
necessary to use somewhat more severe conditions for samples of
very low activity, such as those having a very high silica to
alumina mole ratio. In those instances, a temperature of up to
about 1000.degree. F. and a liquid hourly space velocity of less
than one, such as 0.1 or less, can be employed in order to achieve
a minimum total conversion of about 10%.
The new ZSM-22 highly siliceous zeolite can be suitably prepared
from a reaction mixture containing a source of silica, Q.sub.2 O,
an alkali metal oxide, e.g., sodium, potassium or cesium, water,
and alumina, and having a composition, in terms of mole ratios of
oxides, falling within the following ratios:
______________________________________ Reactants Broad Preferred
______________________________________ SiO.sub.2 /Al.sub.2 O.sub.3
= 20 to .infin. 30 to 1000 M.sub.2/n O/(Q.sub.2 O + M.sub.2/n O) =
0 to 0.95 0.1 to 0.8 ______________________________________
wherein Q.sub.2 O is the oxide form of an organic compound of an
element of Group 5-B of the Periodic Table, e.g., N, P, preferably
N, containing at least one alkyl or aryl group having at least 2
carbon atoms, and M is an alkali or alkaline earth metal of valence
n, and maintaining the mixture at crystallization temperature until
crystals of the new ZSM-22 zeolite are formed. Thereafter, the
crystals are separated from the liquid by any conventional means,
washed and recovered. The zeolite of this invention can be used in
aromatics alkylation reactions (e.g., toluene alkylation by
methanol & ethylene), toluene disproportionation, selective
cracking of a meta/para-cymene mixture and in conversion of various
oxygenates to gasoline-grade hydrocarbons and/or chemicals, e.g.,
olefins.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Crystallization can be carried out at either static or stirred
conditions in a reactor vessel, e.g., a polypropylene jar or teflon
lined or stainless steel autoclaves at 80.degree. C. (176.degree.
F.) to about 210.degree. C. (410.degree. F.) for about 6 hours to
150 days. Thereafter, the crystals are separated from the liquid
and recovered. The composition can be prepared utilizing materials
which supply the appropriate oxide. Such materials include
aluminates, alumina, silicates, sodium silicate, silica hydrosol,
silica gel, silicic acid, sodium, potassium or cesium hydroxide,
and an organic compound. The organic compound contains an element
of Group 5-B, such as nitrogen or phosphorus, preferably nitrogen.
The preferred compounds are generally expressed by the following
formula: ##STR1## wherein J is an element of Group 5-B of the
Periodic Table, e.g. N or P, preferably N, and each R is an alkyl
or aryl group having at least two (2) carbon atoms or hydrogen.
Suitable organic compounds are dialkylammonium compounds wherein
each of the alkyl groups is the same or different and each alkyl
group has two (2) to eight (8) carbon atoms, e.g., ethyl, propyl,
butyl, pentyl, hexyl, heptyl or octyl.The reaction mixture can be
prepared either batchwise or continuously. Crystal size and
crystallization time of the new crystalline material will vary with
the nature of the reaction mixture employed and the crystallization
conditions.
The organic compounds need not be used as such. They may be
produced in situ by the addition of the appropriate precursors.
These precursors comprise either compounds characterized by the
formula RR'R"J where R, R', and R" are selected from alkyl,
substituted alkyl, aryl, substituted aryl, cycloalkyl, substituted
cycloalkyl and hydrogen, and J is an element of Group 5-B, e.g. N
or P, or compounds of the formula R'"X where R'" is alkyl,
substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl and
substituted aryl and X is an electronegative group.
As set forth above, the ZSM-22 zeolite of this invention can be
prepared at a relatively wide range of SiO.sub.2 /Al.sub.2 O.sub.3
ratios of about 20 to about .infin..
While synthetic ZSM-22 zeolites may be used in a wide variety of
hydrocarbon conversion reactions, they are notably useful in the
processes of polymerization, aromatization and cracking. Other
hydrocarbon conversion processes for which ZSM-22 may be utilized
in one or more of its active forms include, for example,
hydrocracking and converting light aliphatics to aromatics, e.g.,
as disclosed in U.S. Pat. No. 3,760,024, the entire contents of
which are incorporated herein by reference. Preliminary results
indicate that ZSM-22 is para-selective in its catalytic
reactions.
Employing a catalytically active form of the ZSM-22 catalyst for
polymerization of olefins containing liquid or gaseous charge
stocks, such charge stocks can be polymerized at temperatures
between 290.degree. and 450.degree. C. (about 550.degree. and
850.degree. F.) at an hourly space velocity of between 0.5 and 50
WHSV (weight hourly space velocity) and a pressure of between 0.1
and 800 psig. In employing the catalyst of the present inention for
aromatization of gaseous or liquid charge stocks which may be
olefinic or paraffinic, with or without aromatics present, such
stocks can be aromatized at temperatures of between 430.degree. and
650.degree. C. (about 800.degree. and 1200.degree. F.), pressures
of 1 to 10 atmospheres and space velocities of between 0.1 and 10
weight hourly space velocity (WHSV).
The ZSM-22 zeolites are also useful in the conversion of oxygenates
(e.g., methanol) to gasoline-grade hydrocarbons or to chemicals,
e.g., olefins. The conversion process can be conducted in a fixed
bed, in a fixed bed tubular reactor or in a fluidized bed reactor.
The prior art processes for carrying out such conversion with ZSM-5
and other zeolites are disclosed, e.g., in U.S. Pat. Nos.
3,894,106, 3,894,107, 3,904,508, 3,907,915, 3,931,349, 3,965,205
and 3,998,898, the entire contents of all of which are incorporated
herein by reference. The ZSM-22 zeolite can be substituted for
other ZSM-5 type zeolites used in the prior art. Accordingly, the
process operating conditions and details will be identical to those
of the aforementioned patents, except that the ZSM-22 zeolite is
substituted in the process for the zeolites of the prior art. In
the fluidized bed reactor, the reaction is carried out at a
temperature of at least 500.degree. F., at pressure of 1 to 200
atmospheres and at 0.5 to 50 liquid hourly space velocity
(LHSV).
In a fixed bed reactor, the process is conducted in two stages. The
first stage comprises conversion of the oxygenates to dimethyl
ether (in a DME reactor), and the second stage conversion of the
first reactor effluent to the hydrocarbon products of the reaction.
Both stages of the reaction are carried out in the presence of a
catalyst: the first stage with a gamma-alumina catalyst (see, e.g.,
U.S. Pat. No. 3,931,349), and the second stage with a ZSM-5 type
zeolite catalyst, or more specifically with a ZSM-22 zeolite
catalyst.
The ZSM-22 zeolite can also be used in catalytic dewaxing of
petroleum stocks. Prior art processes for catalytic dewaxing of
such stocks over ZSM-5 and similar zeolites are disclosed, e.g., in
U.S. Pat. Nos. 3,894,938, 4,222,855, 4,137,148, 3,668,113,
3,755,138 and 4,080,397, the entire contents of all of which are
incorporated herein by reference. The ZSM-22 zeolite of this
invention can be substituted as the catalyst in the processes of
the aforementioned patents. Accordingly, the process conditions and
operating details will be the same as those in the patents, except
that the new ZSM-22 zeolite is substituted in the process for the
catalysts of the prior art. Thus, the dewaxing is usually carried
out by passing the feedstock over the ZSM-22 catalyst, in the
presence or absence of added hydrogen, and the effluent of that
step may optionally be subjected to other conventional refining
steps, e.g., desulfurization and/or denitrogenation. The ZSM-22
zeolite used in the dewaxing process may have incorporated therein
a hydrogen transfer functional component, such as nickel, palladium
or platinum, in the amount of 0.05 to 5% by weight, based on the
total weight of catalyst.
In gas oil dewaxing, the catalytic dewaxing step is conducted at a
temperature of about 300.degree.-1000.degree. F., a pressure of
0-2000 psig, and at liquid hourly space velocity (LHSV) of 0.1 to
10 with a hydrogen to hydrocarbon ratio of about 0 to about
25:1.
In lube stock dewaxing, conditions for the catalytic hydrodewaxing
step include a temperature of between about 500.degree. F. and
about 675.degree. F., a pressure of between about 100 and about
3000 psig, preferably between about 200 and about 1000 psig. The
liquid hourly space velocity is between about 0.1 and about 10,
preferably between about 0.5 and about 4.0, and the hydrogen to
feed ratio is about 400 to about 8000, preferably about 800 to 4000
standard cubic feet (scf) of hydrogen per barrel of feed.
Synthetic ZSM-22 zeolites can be used either in the organic
nitrogen-containing and alkali metal-containing form, the alkali
metal form and hydrogen form or another univalent or multivalent
cationic form. The as-synthesized zeolite may be conveniently
converted into the hydrogen, the univalent or multivalent cationic
forms by base exchanging the zeolite to remove the sodium cations
by such ions as hydrogen (from acids), ammonium, alkylammonium and
arylammonium including RNH.sub.3, R.sub.3 NH.sup.+, R.sub.2
NH.sub.2.sup.+ and R.sub.4 N.sup.+ where R is alkyl or aryl,
provided that steric hindrance does not prevent the cations from
entering the cage and cavity structure of the ZSM-22 type
crystalline zeolite. The hydrogen form of the zeolite, useful in
such hydrocarbon conversion processes as isomerization of
poly-substituted alkyl aromatics and disproportionation of alkyl
aromatics, is prepared, for example, by base exchanging the sodium
form with, e.g., ammonium chloride or hydroxide whereby the
ammonium ion is substituted for the sodium ion. The composition is
then calcined at a temperature of, e.g., 1000.degree. F. (about
540.degree. C.) causing evolution of ammonia and retention of the
hydrogen proton in the composition. Other replacing cations include
cations of the metals of the Periodic Table, particularly metals
other than sodium, most preferably metals of Group IIA, e.g., zinc,
and Groups IIIA, IVA, IB, IIB, IIIB, IVB, VIB Group VIII of the
Periodic Table, and rare earth metals and manganese.
Ion exchange of the zeolite can be accomplished conventionally,
e.g., by admixing the zeolite with a solution of a cation to be
introduced into the zeolite. Ion exchange with various metallic and
non-metallic cations can be carried out according to the procedures
described in U.S. Pat. Nos. 3,140,251, 3,140,252 and 3,140,253, the
entire contents of which are incorporated herein by reference.
The ZSM-22 crystal can also be used as a catalyst in intimate
combination with a hydrogenating component such as tungsten,
vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese,
or a noble metal such as platinum or palladium where a
hydrogenation-dehydrogenation function is desired. Such component
can be exchanged into the composition, impregnated therein or
physically intimately admixed therewith. Such component can be
impregnated in or onto the zeolite, for example, in the case of
platinum, by treating the zeolite with a solution containing a
platinum metal-containing ion. Thus, suitable platinum compounds
include chloro-platinic acid, platinous chloride and various
compounds containing the platinum tetramine-platinum complex.
Combinations of the aforementioned metals and methods for their
introduction can also be used.
Synthetic ZSM-22 zeolite, when employed either as an absorbent or
as a catalyst in a hydrocarbon conversion process, should be at
least partially dehydrated. This can be accomplished by heating the
zeolite to a temperature in the range of about 200.degree. C. to
about 600.degree. C. in an inert atmosphere, such as air or
nitrogen for about 1 to about 48 hours. Simple dehydration of the
crystal can also be performed at lower temperatures, such as room
temperature, merely by placing the ZSM-22 zeolite type crystal in a
vacuum, but a longer time is required to obtain a sufficient degree
of dehydration.
In the case of many catalysts, it is desired to incorporate the new
crystal with another material resistant to the temperatures and
other conditions employed in organic conversion processes. Such
materials include active and inactive materials and synthetic or
naturally occurring zeolites as well as inorganic materials, such
as clays, silica and/or metal oxides. The clays, silica and/or
metal oxides may be either naturally occurring or in the form of
gelatinous precipitates or gels including mixtures of silica and
metal oxides. The use of such additional active material in
conjunction with the new ZSM-22 crystal, i.e., combined therewith,
tends to improve the conversion and/or selectivity of the catalyst
in certain organic conversion processes. Inactive materials
suitably serve as diluents to control the amount of conversion in a
given process so that products can be obtained economically and
orderly without employing other means for controlling the rate of
reaction. These materials may be incorporated into naturally
occurring clays, e.g., bentonite and kaolin, to improve the crush
strength of the catalyst under commercial operating conditions.
Such materials, e.g., clays or oxides, function as binders for the
catalyst. It is desirable to provide a catalyst having good crush
strength because in commercial use it is desirable to prevent the
calalyst from breaking down into powder-like materials. These clay
binders are normally employed for the purpose of improving the
crush strength of the catalyst.
Naturally occurring clays which can be composited with the new
zeolite include the montmorillonite and kaolin family, which
families include the subbentonites, and the kaolins commonly known
as Dixie, McNamee-Georgia and Florida clays or others in which the
main mineral constituent is halloysite, kaolinite, dickite,
nacrite, or anauxite. Such clays can be used in the raw state as
originally mined or initially subjected to calcination, acid
treatment or chemical modification. Binders useful for compositing
with the present crystal also include inorganic oxides, notably
alumina.
In addition to the foregoing materials,the ZSM-22 zeolite can be
composited with a porous matrix material such as silica-alumina,
silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia,
silica-titania, as well as ternary compositions such as
silica-alumina-thoria, silica-alumina-zirconia,
silica-alumina-magnesia and silica-magnesia-zirconia. The relative
proportions of finelydivided crystalline material and inorganic
oxide gel matrix vary widely, with the crystal content ranging from
about 1 to about 90% by weight.
In order to more fully illustrate the nature of the invention and
the manner of practicing same, the following examples are
presented.
In the examples which follow, and elsewhere in the specification,
whenever adsorption data are set forth for comparsion of sorptive
capacities for water, cyclohexane and n-hexane, they were
determined as follows:
A weighed sample of the calcined zeolite was contacted with the
desired pure adsorbate vapor in an adsorption chamber, evacuated to
<1 mm pressure and contacted with 12 mm Hg of water vapor or 20
mm Hg of n-hexane or cyclohexane vapor, pressures less than the
vapor-liquid equilibrium pressure of the respective adsorbate at
room temperature. The pressure was kept constant (within about
.+-.0.5 mm) by addition of adsorbate vapor controlled by a manostat
during the adsorption period, which did not exceed about 8 hours.
As adsorbate was adsorbed by the new crystal, the decrease in
pressure caused the manostat to open a valve which admitted more
adsorbate vapor to the chamber to restore the pressures to the
aforementioned control levels. Sorption was complete when the
pressure change was not sufficient to activate the manostat. The
increase in weight was calculated as the adsorption capacity of the
sample in g/100 g of calcined adsorbent.
EXAMPLE 1
ZSM-22 was crystallized by reacting a silicate solution with an
acid alum solution, both prepared as set forth below.
The silicate solution was prepared by adding, to 281 grams (g) of
distilled water, 10.2 g of the 98.1% by weight sodium hydroxide
(NaOH) solution, and 225 g of Q-brand sodium silicate (a brand name
of sodium silicate comprising, in percent by weight, 28.5%
SiO.sub.2, 8.8% Na.sub.2 0, and 62.7% water).
The acid alum solution was prepared by adding, to 385 g of
distilled water, 18.5 g of sulfuric acid (96.4% by weight), 46.4 g
of diethylamine hydrochloride and 7.7 g of aluminum sulfate
[A1.sub.2 (SO.sub.4).sub.3 .times.14H.sub.2 0].
The silicate solution and the acid aluminate solution were mixed
separately in a Waring blender and then transferred to a
Teflon-lined reactor bomb. The bomb was placed in a silicone oil
bath at 300.degree. F. (149.degree. C.) for 3 days. After 3 days
the bomb was removed from the bath and the contents transferred to
a plastic jar and held for 11 days at room temperature. At the end
of 11 days the reaction mixture was returned to the bomb and
crystallization resumed at 300.degree. F. After a total of 16 days
at 300.degree. F. the bomb was sampled, the sample was filtered out
of solution, water washed and dried. The crystalline product was
identified from its X-ray diffraction pattern, set forth below, as
the new zeolite ZSM-22. Chemical analysis of the product gave the
following results:
______________________________________ SiO.sub.2 97.0% wt Al.sub.2
O.sub.3 1.93% wt Na 0.30% wt N 0.76% wt
______________________________________
Adsorption capacities of the washed, dried and calcined product
were:
______________________________________ water 5.0% wt cyclohexane
0.6% wt h-hexane 3.7% wt ______________________________________
X-ray analysis of the product, as synthesized, revealed that the
crystals have the following X-ray diffraction pattern:
______________________________________ Line 2Theta D(.ANG.) I/IMAX
______________________________________ 1 7.93 11.15 51* 2 8.10
10.91 65 3 8.79 10.06 20* 4 8.94 9.89 7* 5 10.11 8.75 14 6 11.90
7.44 1* 7 12.75 6.94 23 8 13.14 6.74 3* 9 13.88 6.38 4* 10 14.76
6.00 5* 11 15.48 5.72 3* 12 15.86 5.59 4* 13 16.33 5.43 10 14 16.52
5.37 5* 15 17.18 5.16 1* 16 17.73 5.00 1* 17 19.38 4.58 12* 18
20.32 4.37 100 19 20.78 4.27 10* 20 21.56 4.12 12 21 22.11 4.02 7*
22 23.07 3.86 36* 23 23.17 3.84 32* 24 23.73 3.75 19* 25 24.07 3.70
36* 26 24.20 3.68 82 27 24.59 3.62 59 28 25.69 3.47 42 29 26.65
3.35 10 30 26.99 3.30 8 31 27.67 3.22 2 32 28.50 3.13 1 33 29.23
3.06 3 34 29.98 2.981 6 35 30.37 2.943 4 36 30.78 2.905 2 37 32.14
2.785 2 38 32.72 2.737 3 39 33.00 2.714 2 40 34.20 2.622 1* 41
35.62 2.520 20 42 36.00 2.495 2* 43 36.60 2.455 2 44 36.90 2.436 8
45 37.39 2.405 3 46 38.03 2.366 6 47 40.25 2.241 1 48 43.77 2.068 4
49 44.45 2.038 3 50 45.03 2.013 4 51 45.37 1.999 5 52 46.38 1.958 1
53 47.30 1.922 1 54 47.76 1.904 3 55 48.57 1.874 8 56 49.30 1.848 1
57 49.78 1.832 1 58 51.13 1.786 3 59 52.01 1.758 1 60 52.85 1.732 1
61 55.02 1.669 1 62 55.70 1.650 2 63 56.45 1.630 3 64 57.45 1.604 5
65 58.81 1.570 1 ______________________________________ *Intensity
enhanced by ZSM5.
Example 2
In this example the same chemical formulation, i.e., the same
silicate and the alum solutions, was used as in Example 1. The
reaction mixture, obtained by mixing the silicate and the aluminate
solutions, was held for 3 days at 300.degree. F. in the reactor
bomb, then for 7 days at ambient temperature, then for 3 more days
at 300.degree. F., for a total of 6 days at 300 F. The crystalline
product was sampled and the sample was washed and dried according
to the procedure of Example 1. X-ray diffraction analysis of the
sample showed that the crystals had the X-ray diffraction pattern
of the Table in Example 1. The zeolite was determined to be 100%
ZSN-22.
Example 3
In this example the same chemical formulation, i.e., the same
silicate and the alum solutions, was used as in Example 1. The
reaction mixture, obtained by mixing the silicate and the aluminate
solutions, was aged for 3 days at ambient temperature prior to
crystallization in the reactor bomb at 300.degree. F. After 7 days
of crystallization at 300.degree. F. the sample was held for two
days at ambient tempeature, then crystallization was resumed at
300.degree. F. for a total of 12 days at 300.degree. F. The
crystalline product was also analyzed by X-ray diffraction and it
was determined to have the same pattern as shown in the Table of
Example 1. The product was determined to be 105% ZSM-22.
In Examples 4-7, the ZSM-22 zeolite was prepared by an alternative
method using hexanediamine as the organic compound. The full
details of that method are disclosed in a commonly assigned U.S.
patent application of E. W. Valyocsik, filed contemporaneously
herewith, Mobil Oil Corporation's Ser. No. 373452 filed 4/30/82,
the entire contents of which are incorporated herein by
reference.
EXAMPLES 4-6
A solution of 28.6 parts colloidal silica (30 wt. % SiO.sub.2) and
29.8 parts water was prepared. A solution of 1 part aluminum
sulfate (17.2 wt. % Al.sub.2 O.sub.3), 2.3 parts potassium
hydroxide and 52.3 parts water was also made. These two solutions
were combined and mixed for 15 minutes. Five parts of
1,6-hexanediamine were added to the solution and the entire mixture
was stirred. This solution was put into a stirred autoclave and
heated to 320.degree. F. This temperature was maintained for 72
hours.
The resultant zeolite was then filtered and washed on a Buchner
Funnel and then dried overnight at 250.degree. F.
This preparation was prepared three consecutive times and the
analyses are as follows:
______________________________________ Example 4 5 6
______________________________________ Zeolite ZSM-22 ZSM-22 ZSM-22
Crystallinity 120% 140% 135% SiO.sub.2 /Al.sub.2 O.sub.3 Ratio 64
61 64 Na, wt. % 0.13 0.10 0.13 K, wt. % 0.21 0.21 0.22 N, ppm 660
1170 670 ______________________________________
The X-ray diffraction pattern of the as-synthesized zeolite of
Example 5 is set forth below in Table II:
TABLE II ______________________________________ Line 2Theta
D(.ANG.) I/IMAX ______________________________________ 1 8.10 10.91
35 2 8.79 10.07 2* 3 10.11 8.75 7 4 12.71 6.97 11 5 16.23 5.46 4 6
16.47 5.38 8 7 19.35 4.59 11 8 20.30 4.37 100 9 21.75 4.09 2 10
23.05 3.86 8* 11 23.11 3.85 6* 12 24.16 3.68 74 13 24.53 3.63 63 14
25.60 3.48 38 15 26.38 3.38 5 16 26.58 3.35 7 17 26.99 3.30 7 18
27.68 3.22 1 19 29.97 2.982 3 20 30.34 2.946 3 21 30.76 2.906 2 22
32.01 2.796 1 23 32.63 2.744 2 24 32.92 2.721 3 25 35.55 2.525 19
26 36.82 2.441 9 27 37.30 2.411 2 28 37.96 2.370 6 29 39.30 2.293 1
30 40.12 2.248 1 31 43.67 2.073 3 32 44.36 2.042 3 33 44.79 2.024 3
34 45.27 2.003 3 35 47.72 1.906 4 36 48.41 1.880 8 37 49.30 1.848 2
38 51.08 1.788 3 39 51.90 1.762 1 40 52.76 1.735 1 41 54.91 1.672 1
42 55.62 1.652 2 43 56.32 1.634 2 44 57.34 1.607 5 45 58.71 1.573 1
______________________________________ *Intensity enhanced by
ZSM5.
The data of Table II was obtained in the same manner as the data of
Table I. Accordingly, the abbreviations and symbols of Table II
have the same meaning as set forth above in connection with the
discussion of Table I.
EXAMPLE 7
Catalyst Preparation from Zeolites of Examples 4-6
Samples of equal weight of zeolites of Examples 4-6 were combined
and then mixed with alumina and water. This mixture was extruded
into 1/16" pellets and dried. The extruded material contained 65
parts ZSM-22 per 35 parts alumina.
The dried extrudate was calcined for three hours at 538.degree. C.
in flowing nitrogen. After cooling, the extrudate was twice
contacted with an ammonium nitrate exchange solution (about 0.08
lb. NH.sub.4 NO.sub.3 /lb of extrudate) for one hour at room
temperature.
The extrudate was then dried and calcined in air at 538.degree. C.
for six hours. The product analysis is as follows:
______________________________________ Na, wt. % 0.03 N, ppm 17
______________________________________
.alpha. (activity at 1000.degree. F. relative to silica-alumina)
=57
The alpha-test (.alpha.-test) is an indication of the relative
catalytic cracking activity of the catalyst compared to a standard
catalyst. The value of .alpha. is the relative rate constant (rate
of n-hexane conversion per unit volume of catalyst per unit time).
It is based on the activity of fresh silica-alumina cracking
catalyst taken as .alpha.=1.
The .alpha.-test is further described in a letter to the editor,
entitled "Superactive Crystalline Alumino-Silicate Hydrocarbon
Cracking Catalysts", by P. B. Weisz and J. N. Miale, Journal of
Catalysis, Vol. 4, pp. 527-529 (August 1965) and in U.S. Pat. No.
3,354,078, the entire contents of both of which are incorporated
herein by reference.
EXAMPLES 8-10
The catalyst of Example 7 was subjected to a feedstream of 50/50 by
weight methanol and water at 30 psig pressure at 1 WHSV (methanol)
to produce ethylene. The results and conditions of the three
Examples are summarized below.
______________________________________ Example 8 9 10
______________________________________ Temperature, .degree.F. 672
700 725 Methanol Conversion, % by wt. 47.5 60.2 68.8 Ethylene
Selectivity, % by wt. 21.3 17.9 13.7
______________________________________
EXAMPLE 11
Heavy Stock Catalytic Dewaxing
17.6 grams of the catalyst of Example 7 was mixed with 88 grams of
furfural raffinate in a pressure reactor. The reactants were
allowed to react for 130 minutes at 500 psig. The results of the
runs, for a product having boiling point (BP) of 650.degree. F. or
above, are summarized below.
______________________________________ Run Reaction Temp.
.degree.F. Pour Point .degree.F. VI (Viscosity Index)
______________________________________ A 600 90 99.9 B 550 65 106.8
______________________________________
The properties of the feedstock are set forth below. The objective
of this example was the reduction of the amount of high molecular
weight paraffins (waxes) so that the resultant hydrocarbon stock
can be processed into more desireable products. As the above data
indicates, the pour point of the feedstock was reduced
considerably, indicating that ZSM-22 is an effective dewaxing
zeolite.
______________________________________ Feed of Example 11
______________________________________ Gravity, API 29.2 Pour
Point, .degree.F. 105 KV @ 100.degree. C., Centistokes 9.260 KV @
130.degree. C., Centistokes 38.72 Carbon Residue, wt. % (RCR*) 0.11
Sulfur, wt. % 0.74 Nitrogen, wt. % 42. Refractive Index @
70.degree. C. 1.46513 Aniline Point, .degree.F. 233
______________________________________ *Rams Carbon Residue
______________________________________ Vacuum Distillation, % by
Wt. BP, .degree.F. ______________________________________ -- 769 5
825 10 845 30 878 50 897 70 911 90 931 95 937
______________________________________
It will be apparent to those skilled in the art that the specific
embodiments discussed above can be successfully repeated with
ingredients equivalent to those generically or specifically set
forth above and under variable process conditions.
From the foregoing specification one skilled in the art can readily
ascertain the essential features of this invention and without
departing from the spirit and scope thereof can adopt it to various
diverse applications.
* * * * *